Number 201 - February 2000

Enabling Hard Drive Ultra DMA
by Carl Tenning, Tacoma Open Group
When I upgraded to an 8.4GB hard drive, I did not notice at the time that the drive was not operating in the Ultra DMA mode, even though the drive was Ultra DMA/66 compatible.     Ultra DMA is a protocol for transferring data between a hard disk and the computer main memory (RAM). Ultra DMA/33, also known as Ultra-ATA and Fast ATA-2, transfers data at a burst rate of 33.3 megabytes per second. This is twice as fast as the previous protocols using Programmed IO (PIO) Mode-4 or DMA Mode-2. In addition to having a DMA/33 compatible hard drive to use Ultra DMA/33, the computer must also have an Ultra DMA compatible ROM-BIOS, motherboard chip set, and operating system. Windows 98 fully supports Ultra DMA. Ultra DMA/66 came later and transfers data at a burst rate of 66.7MHz. Here again, the computer BIOS and motherboard chip set must support the higher standard.     When I purchased my existing computer in August 1997, the motherboard chip set and ROM-BIOS were both Ultra DMA/33 compatible, but the hard drive and operating system, Windows 95, were not. Therefore the hard drive operated in the PIO Mode-4 protocol. Within the next year or so I upgraded to Windows 98	which was Ultra DMA/33 compatible. However, since the original hard drive was not Ultra DMA/33 compatible, the system still ran in the PIO mode. It wasn't until later that I upgraded to a larger hard drive, which was Ultra DMA/33 compatible. I expected to enable the Ultra DMA/33 operation. I did so by going into the CMOS setup and making the appropriate selections. However, when I checked Windows Device Manager under Disk Drives, Generic IDE Disk Type 46, Properties, Settings Tab, the check box for setting DMA was blank. Every time I tried to check mark the box and re-boot, Windows would remove the check.     What I finally discovered was that the Western Digital hard drive was set for Ultra DMA/66 and not Ultra DMA/33. My motherboard and BIOS were only capable with Ultra DMA/33. Checking the Western Digital web page, I found that they had a utility for resetting the drive from DMA/66 to DMA/33. By downloading and running their utility Lifeguard Tools, I successfully reset the drive to Ultra DMA/33. Now the DMA box in the Device Manager settings remains checked. Running a benchmark on the hard drive, both before and after the change, confirmed that my hard drive data transfer was approximately twice as fast.
Number 201 - February 2000